1. Field of the Invention
This invention relates generally to the field of paper box folding and sealing and more specifically to an apparatus and method for inspecting carton blanks moving along an assembly line using a real time synthetic image processing system for inspecting skived glue, hemming and skew, and backfold of cartons.
2. Description of Related Art
During the manufacture of paper boxes, paper blanks advance along a paper line pathway for diverse folding and gluing or sealing operations. The paper blanks may have "score lines" that divide the blank into sections called "panels" and "flaps". During folding operations, the sections are folded about the score lines to produce the sides, top and bottom of a completed box. In one such folding and gluing operation, a portion of the edge flap thickness is cut away and then folded back on itself. It is then folded into a partially overlapping relationship over central, adjoining panels of a blank along certain score lines. The flaps and panels of the blank are glued or otherwise sealed to produce a completed structure in the form of a folded box. After a paper box has been assembled, a sample of such boxes is tested for defects by observation or by testing in a dark room by shining a light and looking for light passages in the box. These methods are time consuming and do not include 100% testing.
Various video inspection systems are known in the prior art. A box inspection device and method is described in U.S. Pat. No. 5,213,656, issued May 15, 1993, to Michael W. Chang et al. and assigned to Prime Technology, Inc. This patent discloses a box inspection device and method. A quality monitoring system employing vision processing equipment to photograph at least one of the edges of every folded-over box blank as it is conveyed through a box forming machine is used to determine in-line whether the blanks, when unfolded, will produce square boxes having essentially all angles between adjacent box side panels. The electronic images are electronically digitized and the resulting data processed by computer to calculate critical parameters of the folded-over blank, including gap width, longitudinal taper of the gap width, and alignment of the lateral edges of the panels surrounding the gap in relation to the lateral edge of the gap. Comparison of these measured critical parameters with corresponding parameters for an idealized box stored in the computer indicates the quality of the formed box and whether the quality falls within acceptable parameters. However, a video means is used to obtain a picture of a box blank which is then digitized and analyzed. The primary disadvantage of this approach is speed of data acquisition and analysis. At typical line speeds of 2000 belt feet/minute, between 33 to 67 boxes per second would have to be inspected.
U.S. Pat. No. 4,995,091, issued on Feb. 19, 1991, to Hoshimi Shimbara, and assigned to Mazda Motor Manufacturing (USA) Company describes a method and apparatus for identifying marking holes in an object moving along a conveyor or the like, in which television image signals of the identifying marking holes are classified into signals above and below a threshold level voltage and then made into a monochrome image of the identifying marking holes which is then compared with a pre-memorized image of the marking hole. However, this apparatus also cannot operate at the above indicated line speeds.